Sound reproduction



March, 22, 1932" J. WEINBERG'ER SOUND REPRODUCTION Filed Nov 10, 1928 m7 10m 11 M075:

lmlilll INVENTOR Juuus NEINBERGER flalauw ORNEY Patented 'Mart 22, 1932 UNIT D STATES! PATENT orrlcr.

corms wnmnnnona, on NEW Yonx, n. 1., ASSIGNOIt-TO namo oonrom'rronor AMERICA, A. CORPORATION OF IIJIILAW'ABIEv SOUND REPRODUCTION Application filed November 10, 1928. Serial No. 818,411.

One object of this invention is to provide an improved system and means for control= ling the volume of sound in the reproduction from a talkin motion picture film.-

Another object of this invention is to provide means for causing an apparent shift in the source of sound emanating from the locality of a movie screen so as to give the eifect of a change in location to the sound coming from the reproducers.

A further object is to provide an improved method" for reproducing sounds recorded upon a film.

Other objects of this invention will become apparent from the following specification taken in connection with the accompanying drawings.

This invention concerns films carrying a plurality of records, each record being designed to serve a special purpose. The systerms for reproducing such a film are designed to properlyutilize the purpose of each of the At present one of the greatest difficulties in talking moving pictures lies in the fact that the sound record on the film must be recorded at such an intensity that it is always stronger than the ground noise. The latter being the noise which is heard in the reproducing loud speakers due to irregularities in the filmstructure and dirt, corresponding to the scratch on a phonograph record. On the other hand, the limit of depth or darkness with which a sound can be recorded is fixed by the photographic emulsion properties. In a general way, therefore, the ratio of maximum to minimum loudness which can be employed is quite small and is not comparable with the normal ratio employed in the rendition of music, such as, for example, by a symphony orchestra.

Furthermore, a single instrument or voice is usually and necessarily recorded on the film at the same intensity as a large orchestra in order to obtain a good ratio of intensity to ground noise. This requires the operator of the reproducing mechanism to adjust the amplification of'his loud speaker amplifiers to a suitable intensity for each film record, so

as to secure reproduction of natural loudness. In this connection the invention. relates to a Where a number of different performers are recorded on the same record or where, for example, the intensity varies wldely from one portion of the film record to another with respect to the intensity of the original, an even greater burden is placed on the reproducing operator who must be somewhat of an artist to suitably vary the gain of his reproducing amplifier.

It is the object of this invention to overcome each of these difiiculties. This is in part done by recording a second record which I term a volume control record upon the film. The function of this record is merely to actuate some device, as for instance, the reproducing amplifier in order to vary its gain in accordance with the desired variation in the loudness of reproduction.

For example, the volume control record may vary the voltage impressed upon the grid of a vacuum tube which is so connected in an amplifier circuit as to cause the gain of amplification to vary in proportion to the voltage or even in a greater proportion. Such a tube might, for instance, be used as a variable resistance in a resistance coupled amplifier. Other methods of carrying out this invention will readily be appreciated by those skilled in the art.

The Volume control record may be made either manually by an operator while recording the sound or automatically by using the natural variation in loudness of the sound produced by the performers orchestra. It may also be made at a later date by the orchestra, leader who directed the original presentation or by another person.

Similar processes to these are used in the recording of piano records for reproduction on automatic player pianos wherein a line is printed on the paper roll which, when followed by the pointer in reproduction, varies the loudness.

This invention also deals with an additional record to be placed upon the film to be used in conjunction with moving sound reproduction. Here the additional record has the function of controlling the position of the sound.

position control record which has for its purposethe switching of the sound recording on the sound record to each of several loud speakers which may be located as desired, 1n order 5 to cause the illusion of movement of the to feed the several loud speakers This is also accomplished by volumecontrol tubes which will be described more in 15 detail hereinafter.

Each loud speaker would have associated with it, its own am lifier and the gain of these amplifiers wou d be controlled by the volume control tubes. Each 'volume control tube would be actuated by 50 some particular type of impulse or some par- 65 cycles, t

,ticular frequency, and the amplifier with which it was associated brought into action when the respective volume control is so actuated.

It is apparent that a record may be made containing three parts. One, is the usual sound record recorded in the desired level with respect to the ground noise, varying in intensity in accordance with the original or any desired ratio. Two, is a volume control record which controls the actual variation in loudness of reproduction through vacuum tubes which actuate and cause the gain of the amplifiers to be varied. And three, is a position control record which causes the sound record currents to be smoothly shifted from one loud speaker to another or to a-number of loud speakers in orderto cause apparent moving sound reproduction to occur. All of these records may. be printed on the same film together with and synchronized with motion pictures.

Having thus briefly described my invention attention is invited to the accompanying drawings in which:

Fig. 1 shows a diagram for carrying out that part of my invention which relates to volume control, and;

Fig. 2 shows a diagram for carrying out that part of my invention which relates to position control.

Referring now more particularly to Fig. 1 there is shown at a source of light which is caused to pass through a moving film 11 upon which 1s recorded the volume control record 12. The light passing through the film 11 and through the usual slot or aperture 13 falls upon the photoelectric device 14 which may be of any usual or well known type and may be biased by the batterv 15 through the resistance 16 in the usual and well known manner.

The volume control record may be in the form of pulsations of a frequency of say 1000 e amplitude of which is varied in the manner in which it is later desired to vary the volume of the audio freqiiiienc output of the amplifier which ampli es t e reproduced sounds. The 1000 cle note is amplified by means of the amp ifier 17 and rectified in the rectifier 18 both of which are of the usual well known construction. The rectified D. C. output of the rectifier 18 is filtered in the filter 19 and impressed across .a resistance 20 in the input circuit of the volume control tube 21. It is understood that this D. C. voltage across the resistance 20 will vary in accordance with the volume it is desired to re roduce and thus the internal resistance 0 the volume control tube 21, which will vary in accordance with the input voltage, varies in proportion to the desired amplification.

As the grid bias of the control tube is varied its internal resistance variesand this causes it to act as a variable resistance in parallel with the plate. circuit resistance 22 of the am lifier device 23 and thereby vary the ampli cation of the latter by varying the flow of current throu h the resistance and thereby the elfective p ate voltage. The audio frequency input to the amplifier device 23 is shown at 24 as impressed upon the grid of the amplifier 23. This first amplifier tube may be followed by other amplifier tubes and thllsthe amplification of the system is varied by the volume control record on the film.

Referring now more particularly to Fig. 2 the light from the source is caused 'to as through that portion of the film 11 hich bears the position control record 31 and is focused through the slot or a rture 32 upon the photo-electric cell 34. The: ition control record consists of several sudio frequencies each of which will cause a variation in the gain of the amplifier system associated with a given loud speaker, or a given group of loudspeakers. For example, the position control record as shown in Fig. 2 comprises two parts a and b, the former of which comprises a 500 cycle tone and the latter of which comprises a 1000 cycle tone. This frequency occurring in the output of the hoto-electric device 34 is amplifiedin the au '0 frequency amplifier 35 and distributed to the rectifiers 36 and 37 throu h suitable connections which may or may not e similar to those illustrated for pu oses of this disclosure. The input of the rectifier 36 comprises a tuned transformer 48 which is tuned to a frequency of 500 cycles whereas the input to the rectifier 37 com rises a similar tuned transformer 49 tun to a frequency of 1000 cycles. Between the rectifier 36 and the volume control tube there is interposed the low-pass filter 38 and similarly the low-pass filter 39 is interposed between the rectifier 37 and the volume control tube 44. The output of filters 38 or39 is impressed as a negative biasing voltage on the grids of tubes 40 or 44.

*mum amplification of the audio frequency input 42 with respect to the reproducer 43. At the same time as no energy passes through the filter39 to the volume control tube 44 maximum current will flow through volume control tube 44 and minimum amplification will occur in the amplifier 50 and the output of reproducer 51 will be at a minimum.

Similarly, when that part of the distribution control record which is designated at 6, having a 1000 cycle frequency, is between the light source 30 and the photo-electric cell 34, the audio frequency input at 42 will be amplified almost exclusively by the amplifier 50 and the sound reproduced through the medium of the reproducer 51.

It is obvious that both the records 12 and 31 as well as the actual sound record (not shown) are side by side on the same moving film but for the purpose of simplicity have been shown as separated. It is also obvious that the corresponding pictures are opposite the other records as explained above.

Having thus carefully described my invention it is to be understood that I am not to be limited by the specific embodiments shown and described for purposes of illustration but by the scope of the appended claims.

. Claims:

1. The process of volume control which comprises producing a photo-electric record of a constant frequency oscillating current, the amplitude ofwhich is varied in accordance with desired sound intensity, reproducing said oscillatory current, amplifying said oscillatory current, rectifying said amplified oscillatory current, filtering said rectified oscillatory current, producing a photographic sound record of the sound desired to be reproduced, reproducing said sound, amplify ing said reproduced sounds, and varying the amount of amplification in accordance with said first mentioned rectified oscillations.

2. The process of volume control which comprises, reproducing, from a record, a constant frequency oscillating. current, the amplitude of which is varied in accordance with the desired sound intensity, producing a sound the volume of which it is desired to control,'amplifying the volume of said sound, and controlling the amount of amplification in accordance with'th'e amplitude of the constant frequency oscillating current.

3-. The process of volume and sound position control which comprises producing a photo-electric record of constant frequency oscillating current, the amplitude of which is varied in accordance with desired sound intensity, reproducing said oscillatory current, amplifying saidoscillatory current, rectifying said am lified oscillatory current, filtering said rectified oscillator current, producing a photo-electric soun record of the 7 sound frequencies desired to be reproduced, reproducing said sound frequencies, amplifying said reproduced sound frequencies, varying the amount of amplification in accordance with said first mentioned rectified 7 oscillations, producing a photo-electric record of one of several constant amplitude audio frequencies, reproducing said last mentioned audio frequencies, amplifying said aud1o frequencies, filtering the respectiveifreso quencies and controlling the distribution of said amplified sound frequencies in accordance with the frequency of said last named frequency.

4. The process of volume control which 35 comprises producing a constant frequency osclllatingcurrent the amplitude of which is varied in accordance with the desired sound lntensity, producing a sound the volume of which it is desired to control, amplifying the volume of said sound, controlling the amount of amplification in accordance withthe amplitude of the constant frequency oscillating current, producing one of several constant amplitude audiofrequencies and controlling the distribution of said amplified sounds in accordance with the frequency of said constant amplitude audio frequency.

5 The process of sound position control which comprises producing a photo-electric record of one of several constant amplitude audio frequencies, reproducing said audio frequency, amplifying said audio frequencies, filtering the respective frequencies, producmg a photo-electric sound record of the sound desired to be reproduced, reproducing said sound, amplifying said reproduced sounds, and controlling the distribution of said amplified sounds in accordance with the frequency of said filtered constant amplitude no audio frequency.

6 The process of sound position control which comprises producing constant amplitude oscillations of different audio frequencies, producing a sound frequency the distribution of which it is desired to control, amplifying .said sound frequencies, and controlling the distribution point of said amplified sound frequency in accordance with the frequency of said constant amplitude oscillations.

7. Apparatus for the control of sound volume which comprises in combination, a moving film having impressed thereon a photoelectric record of sound impulses, a second photo-electric record of constant frequency oscillations, the amplitude of which varies in accordance with the desired sound volume, photo-electric means for converting said last mentioned oscillations into a variable D. C.

potential, means for converting the photoelectric sound record into audio fre uencyimpulses, means for amplifying sai impulses and means for varying the amount of amplification in accordance with said D. C. potential.

8. A aratus for the control of sound volume w ich comprises, in combination with a movin photo-electric record and means for reprod ucing the sound recorded on said records, a second moving of a constant frequency oscillating current, the amplitude of which varies in accordance with the desired sound intensity, means for amplifying the volume of the sound it is desired to control, and means for controlling the amount of amplification in accordance with the amplitude of the constant frequency oscillating current, recorded on said second photo-electric record.

9. Apparatus for the control. of sound which comprises in combination with a photoelectric record of the sound to be controlled, a second photo-electric record, of a constant frequency oscillating current the amplitude of which varies in accordance with the desired sound intensity, photo-electric means for re roducing the oscillatory current recorde b said record, means for amplifying said osci latory current, means for rectifying said amplified oscillatory current, filtering means for said rectified oscillatory current, photo-electric means for reproducing the sound frequencies which it is desired to control, means for amplifying said reproduced sound frequencies, means for varyin the amount of amplification of said soun frequencies in accordance with the said rectified oscillatory current, a third photo-electric record of one of several constant amplitude audio frequencies, means for reproducing said audio frequency, means for amplifying said audio frequenc means for filtering the respective audio requencies, reproducing means located at spaced points, amplifying means for each of said re roducing means, said amplifying means a apted to be supplied by said amplified sound frequencies, and thermionic means for controlling the amplification of each of said last mentioned amplifying means in accordance with the current passing through said last mentioned filter means.

10. Apparatus for the control of audio frequency reproduction which comprises, means for producing a constant frequency oscillating current the amplitude of which is varied in accordance with desired sound intensity, means for producing an oscillatory current representing a sound the volume of which it is desired to control, means for amplifying the volume of said sound, means for controlling the amount of said amplification in accordance with the amplitude of the said constant frequency oscillating current,-means photo-electric record for producing one of several constant amplitude audio frequencies, several sound reproducin means, and means for controlling the distri ution of said amplified sound in accordance with the frequency of said constant amplitude audio frequency.

11. A paratu's for the control of the apparent ocation of sound which comprises in combination with several re roducing units, a photo-electric record of o e of several constant amplitude audio frequencies, photo-electric means for reproducing said audio frequencies, means for amplifyin said audio fr uencies, means for filterin t e respective requencies, a photo-electric sound record, photo-electric means for reproducmg said sound, means for amplifying said reproduced sounds, and thermionic means for controlling the distribution of said am lified sound impulses to the several repro ucin units in accordance with the frequency'o said filtered constant amplitude frequencies.

12. Apparatus for selectively controlling the position of sound which comprises in combination with several reproducing units, means for producing constant amplitude oscillations of different frequencies, means for producing a sound frequency, the position of which it is desired to control, means for ampli ing said sound frequencies for each of sai reproducing units, and means for controlling said amplifying means and thereby the reproducing unlts in accordance with the frequency of said constant amplitude oscillations.

13. The process of sound position control in the reproduction of sound hotographical ly recorded on a strip record aring medium which comprises re roducing the sound recorded and selective y distributing the sound thus produced in accordance with a supple- Iilentary photographic record carried by the 14. The process of sound position and volume control in the reproduction of sound photographically recorded on a strip record bearing medium which comprises reproducing the sound recorded. selectively distributing the sound thus produced in accordance with a supplementary photographic record, and controlling the volume of sound also by said supplementary record.

15. The. process of sound position and volume control in the reproduction of sound photographically recorded on a strip record bearing medium whichcomprises reproducing the sound recorded, selectively distributing the sound thus produced in accordance with a supplementary photographic record carried by the film, and controlling the volume of sound also by said supplementary record.

16. The process of sound position control in the reproduction of sound photograph-ically recorded on a strip record bearing medium which comprises reproducing the sound recorded, selectively and photo-electrically dlS- tributing the sound thus produced in accordance with a supplementary record.

17. The process of sound position control in the reproduction of sound photographically recorded on a strip record bearing medium which comprises reproducing the sound recorded, selectively and photo-electrically d1stributing the sound thus produced in accordance with a supplementary record carried by the film. I

18. The process of sound position and volume control in the reproduction of sound photographically recorded on a strip record bearing medium which comprises reproducing the sound recorded, selectively and photoelectrically distributing the sound thus produced in accordance with a supplementary record, and photo-electrically controlling the volume of sound also by said supplementary record.

19. The process of sound position and volume control in the reproduction of sound photographically recorded on a. strip record nearing medium which comprises reproducing the sound recorded, selectively and photoelectrically distributing the sound thus produced, in accordance with a supplementary 3o record carried by the film, and controlling the volume of sound also by said supplementary record.

20. Apparatus-for the control of the apparent location of sound which comprises in combination with several reproducing units,

a photo-electric record of one of several constant amplitude audio frequencies, photo-electric means for re roducing said audio frequencies, means f dr amplifying said audio frequencies, means for filtering the respec tive frequencies, a photographic sound record, photo-electric means for reproducing said sound record, means for amplifying said reproduced sounds, and relay means for controlling the distribution of said am lified sound impulses to the several repro ucing units in accordance with the frequency of said filtered constant amplitude frequencies.

21. The process of sound position control which comprises producing constant amplitude oscillations of different audio frequencies, producing a sound frequency, the distribution point of which it is desired to control, amplifying said sound frequencies, and

5;; selectively controlling the distribution point of said amplified sound frequency in accordance with'the frequency of said constant amplitude oscillations.

JULIUS WEINBERGER. 

